1. Field of the Invention
This invention concerns a non-contact positioning device which adjusts the position of a driven body by using magnetic force to suspend it.
2. Discussion of Background
In the past, in positioning devices, there were limitations of degree-of freedom when driving. Therefore, when attempting to drive with more than 2 degrees-of freedom at the same time, it was general to use a combination of multiple drive units with fewer degrees-of-freedom. As driving methods for these types of positioning devices, either direct drive by drive sources such as linear motors and solenoids, or indirect drive methods via power transmission components such as gear-wheels and reduction gears were used. Also, the suspension of the drive body was carried out by oil bearings, ball-bearings, air bearings and springs.
However, these types of positioning devices had the following problems. Firstly, since they were composed of combinations of multiple drive units, the construction was complex and large numbers of parts were required. Production was therefore extremely difficult. Secondly, since friction occurred in all parts when driving, besides the emission of heat and fluctuation of output, they became unstable due to wear and it was difficult to ensure accuracy and reliability. Thirdly, since lubrication of the bearings which suspended the driven body was required, prolonged use became impossible in special environments such as the high vacuum of space.
As opposed to this, there are the types of device stated in U.S. Pat. Nos. 4156548 and 4088018. These were devised for the purpose of supporting telescopes in space-craft in isolation from the space-craft's vibration and for correcting the telescopes' optical axes, and discs were supported from their outer perimeter by 6 sets (12) of electromagnets. A 5 degree-of-freedom drive was thus achieved.
However, since in this type of prior device, 2 electromagnets were required for a 1 degree-of-freedom drive, when positioning using a multi-degree-of freedom drive, large numbers of electromagnets had to be used. Moreover, it was necessary to design electromagnets suitable for the respective degrees-of-freedom, and since their shapes and sizes differed, there were problems with difficulty in the arrangement of the electromagnets and complexity of construction.